Cleaning Iron Tsuba
Most tsuba should just be left alone. Any tsuba that is already in good condition should absolutely be left as is. The need to leave our mark shows itself in the habits of collectors who routinely over clean, polish and in the worst cases actually strip the guards they encounter to bare metal in order to apply a new color of their own liking. Remember that the supply of genuine old tsuba can only get smaller. After surviving actual use and hundreds of years of storage, we don’t need to lose any more tsuba to “good intentions.”
So, if you're looking at an iron tsuba with obvious crud and/or red rust, here is a path you can take. Please be very cautious. Go slow. Don't take shortcuts. Ask me if you have any questions.
The simplest and safest first step is to wash your tsuba in mild soap and water. Use hand soap, not detergent or cleanser. Over years of careless handling a tsuba can pick up quite a bit of plain old dirt. After you’ve washed the piece, be sure to dry it thoroughly. Once it’s relatively clean, take a careful look at the piece in good light - sunlight if possible. You’ll probably see plenty of red rust. You may also see various surface coatings of modern to antique origin – wax, shoe polish, paint, old lacquer, etc. If you are not sure what you’re looking at, show the tsuba to someone familiar with old guards. My preference is to leave old lacquer in place, unless it is associated with serious corrosion.
Dealing with crud that won’t come off with soap and water can require a couple of different approaches. The most straightforward method for an iron guard is to boil it in distilled water for 20 minutes or so. This will remove most films without altering the metal or removing any lacquer that may be present. I don’t recommend adding any chemical agents to the water. The more aggressive the cleaning solution the greater the risk of permanently damaging the guard. Boiling water is good enough.
When the tsuba comes out of the water, the good news is that all of the oils and waxes that were hiding rust will be gone. The bad news is that you are likely to be looking at a very ugly, dry, rusty plate at this point. You may wish that you had just left things as they were, and frankly, if you’re not willing to go through with the very time consuming and finger-tiring next step of rust removal, you should have left well enough alone.
Rust removal is a mechanical process of dealing with two slightly different iron oxides. The idea is to rub off the active red corrosion (anhydrous ferric oxide) while leaving behind the slightly harder protective black magnetite patina. I have tried bone, antler, ivory, bamboo, etc., and all are good for certain aspects of the job. I find that ivory (old piano keys are a good source) works best. If it isn’t available, get a section of dense bone. The typical beef “soup bone” is good. Get one that has all of the grease cooked out and use a hammer and chisel (wear your safety glasses) to break the bone up into a number of variously shaped and sized chunks. You’ll find that one of the assortment of sharp and dull surfaces and angles should do the job.
Whatever the tool, you're looking for something harder than the red rust and softer than the patina. Never use steel, iron, glass, sandpaper, or anything else harder than the patina. DO NOT try chemical rust removers - they will remove the patina and damage the iron. In fact don't try chemical treatments of any type - including boiling in tea or anything of the sort. Also, don't put your tsuba in a fire despite what Robinson's “Arts of the Japanese Sword” says! Some people will use chogi oil at the start of the process to loosen the red rust. I haven’t found this method to be much help. It certainly won’t harm the iron, but it is fairly tricky to keep the oil from soaking into the rust inside any sukashi openings and darkening it to an unnatural color.
The surest method is to just take your bone, antler or ivory and gently scrape away at the red rust. Periodically wipe off the red dust to see how you're doing (a damp cloth removes the dust better than a dry one). It’s usually best to work slowly in a small area. Quickly rubbing over a large area is ineffective. Avoid the temptation to find a faster way, because if you do, you will also have found a way to take the patina off. I can't stress this enough. In your inevitable attempt to get the job done faster, you will be tempted to use brass or copper, but it's much too easy to wind up damaging the patina this way. Even if you're successful (this time), you'll have to find a way to get the ugly brass residue off. Lots of patience and tired fingers is the only way. Depending on how severe your rust is, in hours to weeks you will eventually remove the red and just leave the nice black. Go gently and slowly and check your work constantly. Too much scrubbing even with a soft tool will eventually remove the patina.
If you think you've got the rust under control, take your tsuba out in the sunlight and have another look. Most artificial lighting hides red rust somewhat, but sunlight will reveal all. You will probably find that there is still more rust there, but don’t get carried away with trying to remove every trace. Don't over do your cleaning. The idea is not to make a 500-year-old tsuba look new. Older tsuba can have quite a lot of oxide build up that is best left alone. The idea is to remove any active corrosion and restore the beauty of the surface, not to alter fundamentally alter it. An over cleaned tsuba is always worse than an under cleaned one. If you overdo it and damage the patina, you're in trouble. You won't get it back any time soon. There are people who repatinate iron tsuba, but the only one in the US that does good work is no longer taking orders. Many people who claim to do restoration will destroy your guard. Unfortunately, even the best repatination cannot recreate the original aged surface.
Also, NEVER clean the inside of the sukashi. Cleaning the inner walls of the sukashi is like polishing the nakago of a sword – a bad idea. However, do remember to clean the rim as well as the web of the plate.
Once you have the rust down to the point that you're satisfied, get out a piece of cotton cloth and just rub the tsuba. As you keep this up you'll find that the color will darken and the surface will take on a soft luster. The cloth won't do much to remove red rust, so if you find that you missed some rust, go back to more boning. Just go slowly. Once the tsuba is clean, you may want to carry it in your pocket for a few weeks in addition to rubbing it with the cloth. The idea is not to polish the guard to the point that it shines. Also, avoid rubbing the guard on carpeting or synthetics that can leave a greasy finish.
I prefer to stay away from oil on a finished guard. The oily sheen is not as attractive as the natural finish and it will tend to attract dust and lint over time. It will eventually dry out, and can then actually promote a new layer of rust under the dry oil film. By the way, a coat of oil is often used as a “quick fix” to make red rust look dark. This may seem like an improvement in the short term, but really just winds up making the tsuba look like oily dirt. Also, a coating of black shoe polish is a frequently encountered “magic patina.” Watch out for these dirty tricks when buying tsuba.
There's no substitute for spending a lot of time with bone and cloth to get a rusty tsuba into shape. Once you've conquered rust, store your guard in one of the wood boxes made for tsuba. Compared to the cost of all of the work you've just done, the box is cheap. After a fresh sword polish, who would leave that blade out on the shelf, or wrapped up in paper, rather than pay for a shirasaya? Be aware that most of the tsuba boxes you will come across have the center post attached by two very sharp nails coming up from the bottom of the box. Transporting tsuba in this type of box will eventually cause the center post to come loose from the weight of the tsuba moving around on it. Once that happens, the tsuba will rattle around on top of those little nails and scratch up the seppa dai. Always transport tsuba in cloth bags.
Periodically take your tsuba out and give it some light rubbing with the cloth. Try to keep your fingers off, since you risk starting more rust this way.
When I was discussing the initial cleaning, I mentioned that there are a couple of alternatives to consider. In the case of a guard already in good condition, free of rust, etc., but simply covered in wax, it is usually possible to safely remove the wax by rubbing with some isopropyl alcohol.
Additionally, you will occasionally come across a guard that has been coated in polyurethane or some other tough, modern finish. For these, there is a commercial stripper called Strypeeze that will not harm the iron or patina. It could harm you, though, so wear gloves and work with plenty of ventilation and/or a solvent respirator.
Other problems that you can encounter include fire scale, a depatinated plate, cracks and breaks or other serious damage. Unfortunately, these will require professional care. Experimenting with home treatments will generally result in further damage to the plate.